1. Field of the Invention
The invention relates to an adjustable height post for a volleyball net and in particular for a beach volleyball net comprising a ground sleeve anchored in or on a subsoil; and a net pole, which is lockable in variable positions of height, and which is displaceably guided in the ground sleeve, telescoping in the vertical direction, the net pole and the ground sleeve being roller-seated relative to each other by means of bearing rollers.
2. Background Art
A post of the generic type is known from DE 40 19 610 A1. A similar post is described in DE 35 23 568 A1.
As everybody knows, volleyball nets--and of course also badminton nets etc.--are mounted between two posts unless other possibilities of fastening the net are available for instance in a building.
Since different net heights are required for men's and women's volleyball, the posts must be made adjustable in height. Height adjustability is important also in beach volleyball, because in this case a sand bed, the height of which can vary from case to case, is deposited on a solid subsoil. Since the post stands on the solid subsoil, the net must be adjustable in height for the required height distance of 2.50 m between the upper edge of the net and the surface of the sand bed to be set accurately.
Adjustable height posts are known to be used to this end, having a ground sleeve to be anchored in or on the ground and a net post displaceably guided in the ground sleeve, telescoping in the vertical direction, and lockable in variable positions of height.
Problems posed by the known adjustable height posts reside in the fact that a comparatively high operating force is necessitated by the sliding guide used of the pieces that are movable relative to each other. In particular, it is necessary, at the beginning of an adjusting motion, to overcome the static friction existing between the constructional elements.
Furthermore, the known height adjusting mechanisms have the drawback that when the net is fully tensioned, height adjustment is possible only at an unreasonably high expenditure of force or not at all, owing to the bearing and guide construction, because the net pole itself is braced relative to the ground sleeve by the tension of the net. In this regard, adjustment of the net height has been rather complicated and could be attained only by releasing the tension of the net, adjusting the height and then tensioning the net as before.
In connection with beach volleyball, further problems reside in the fact that the sliding mounting of the adjustable height net pole relative to the ground sleeve is highly sensitive to penetrating sand particles and dust deposits, to which it reacts by still increased operating force being needed for the vertical displacement of the net pole or even by blocking.
Finally, the net pole must be designed for corresponding stability and resistance conditioned by the high tension of the net so that the net pole itself together with the net means a considerable weight in particular when being pushed up. Since, as a rule, a locking mechanism must be released for adjustment, one would have to hold the post by one hand, which is too much for many people.